Crossing That Line
by United States of Awesomness
Summary: When Uther dies and Arthur is crowned the King of Camelot, the pressure of being a ruler begins to get to him. He begins making bad choices and Merlin can no longer bear to be by his side anymore. But what will happen when Arthur only gets worse after Merlin leaves? What will Merlin do? Dark!Merlin Caution: Will include non-graphic torture, OC death, and boy x boy smut
1. Chapter 1

Merlin covered his face with his pillow as the morning light stabbed his eyes. He sighed heavily, sitting up in his bed and trying to rub the heavy feeling out of his eyes. He left his room, grabbing an apple off of the shelf and leaving Gaius to sleep in, the man deserved it.

Leaving his chambers, he made his way up to Arthur's, knowing the prince would be pissy if he didn't get his breakfast. Merlin idly ate away at his apple as he retrieved a plate of food from the kitchens, bringing it up to Arthur's room. He put the food on Arthur's table, walking over to the drapes and pulling them open, "Rise and shine,"

He could hear Arthur groan as he woke up, pulling the covers over his head. He walked over to Arthur, knowing he didn't have the strength to pull the blanket off of him so instead he whispered a spell that yanked the plush blanket onto the floor.

"Hey!" Arthur complained, sitting up and sending Merlin a half hearted glare.

"It's not my fault the baby prince missed his afternoon nap yesterday," Merlin teased, laying out Arthur's clothes for the day and helping him dress.

"You know I think the stables need mucked out," Arthur said as he pulled on his last article of clothing, sitting down at the table and looking at his food, "What is this? There's barely anything here," He complained, gesturing to his plate that consisted a loaf of bread, some cheese, and a few grapes.

"Perhaps the kitchens think you're getting fat," Merlin said, a small grin making its way onto his face. Arthur threw the loaf of bread at Merlin, missing him by just inches, "You see? Your throwing is off, that's a sign of weight gain," Merlin said, picking up the bread and holding it out, "Did you want that?"

"Not anymore, lord knows where your hands have been," Arthur said with a scoff, picking at what was left of his breakfast. He pushed his plate away once it was empty, standing up and grabbing his sword, sheathing it on his belt, "You need to wash my clothes and polish my armor and don't forget to write up a speech for me for the round table's anniversary." He said, briskly walking out of the room to leave his servant to his chores.

Merlin sighed, rubbing his temples before getting to work, he had long since accepted that Arthur would never be grateful for how hard he worked but it was beginning to grate on his nerves. He shook his head as he made his way towards the armory, deciding that polishing would be the first thing on his ever growing list of chores.

* * *

"Arthur, think about what you're doing, what will your people think of this?" Merlin said, desperately trying to get Arthur to see reason as he followed the man into his chambers. Ever since the death of his father, Arthur's heart had been closed off to magic but he never imagined the newly crowned king to go this far.

"What else am I supposed to do? Leaving a sorceress to do whatever she pleases will cause nothing but destruction," Arthur said, finally turning around to face Merlin with steely eyes.

"We don't even know if there _is_ a sorceress in Monue, it was just a rumor that some _hunter_ brought to you," He said, trying to reason with the man. It clearly wasn't working as Arthur just shook his head and went to sit behind his desk.

"You know nothing of important matters, Merlin. You're a servant, you polish armor and make beds, so please, stick to what you know," Arthur said, clearly done with having this conversation.

Merlin was taken aback, it wasn't like Arthur to just disregard him as a simple servant. They had been through too much together for Arthur to ever truly believe he was _just_ a servant, but Arthur wasn't exactly in his right mind at the moment. Merlin gave him a silent bow, leaving the room without another word. Clearly Arthur didn't want to talk to him anymore and Merlin was beginning to have the same feeling.

A bad mood was just about oozing out of him as he walked through the corridors of the castle. A few knights on patrol gave him an odd look as they passed but they didn't say anything to him, it wasn't until he passed Gwaine that someone finally spoke to him.

"Merlin! Settle something for us!" The chipper man said as he dragged a fellow knight, Elyan, with him, "Which one of us do you think would stand a better chance picking up a tavern lady while drunk?" Elyan looked like he had no idea how he had gotten into this conversation and wanted nothing more than to get out of it.

Merlin stopped, his bad mood having halted now that he was being assaulted with his friend's rambunctious behaviour, "Definitely Elyan, you would be chugging down glass after glass and not noticing him be the smarter man and sipping his drink," He said, knowing that Gwaine had no self control when it came to liquor.

"So you're saying he'd only win if he cheated, knew you'd back me up," Gwaine said with a grin, not at all phased that Merlin had sided with Elyan as he dragged said knight back to their post.

Merlin shook his head with a small smile, unsure how Gwaine had managed to cheer him up without even knowing anything was wrong. He went back to his chambers, finding Gaius there, treating a boy who looked sick of a fever. "Is he alright?" Merlin asked with concern.

The old man looked up at him, then back at the boy, "Yes, he'll be fine after a good night's rest but I need to look after him,"

"Do you need any help?" Merlin asked, always having been quick to offer his services. If there was somewhere he could be useful he saw no reason why he shouldn't go there.

"Ah, if you could go to the outskirts of town and find me some herbs, that would be wonderful," Gaius said, grabbing a piece of parchment and a pen, writing down what he needed and handing it to Merlin.

The sorcerer skimmed over the list, judging what he had to gather and how long it would take, "I'll be back before nightfall." He said, picking up an empty basket and making towards the door.

"Merlin," Gaius interrupted, stopping him in his tracks and making him turn around. "You need to know that none of the choices Arthur is making are your fault." He said.

Merlin was caught off guard by the statement but soon reasoned that Gaius had heard of the attack Arthur had ordered on the town of Monue. He frowned slightly as he thought back to the night that he had come oh so close to opening up Arthur's heart, if only he had noticed Morgana's little present that she had left on Uther. "I know…" He ultimately knew that it was Morgana's fault that Uther had died but he knew that he could have prevented it if he had been just a little bit more observant. He gave a soft sigh before turning back around and walking out the door.

* * *

"Merlin!" Arthur called as he walked into the physician's chamber later that night, having returned to his own chambers exactly the way he had found it that morning, which was not a good thing.

Merlin was holding a spoon halfway between him and a bowl of soup when Arthur bursted in, looking up at the King with a twinge of hidden irritation, "Yes, my lord?" He asked with a lingering bite in his voice.

"Why is my chamber's a mess? Is it not your job to clean it?" Arthur asked, crossing his arms as he stared at Merlin with that look that he hated so much.

"Sorry, it must have slipped my mind," Merlin said, knowing that no matter what he said, he was going to get the same answer.

"That's no excuse, you had all day to tidy up, what were you doing then?" Arthur prompted.

"I'm afraid that was my fault," Gaius said, stepping into the room and pulling the curtains closed that his the boy whom was still recovering, "I had him gather herbs for me today,"

"So, in other words," Arthur started, "He was at the tavern,"

Merlin's jaw clenched as he forced himself to take slow breaths in order to not yell at Arthur. He just kept repeating him his mind that Arthur was the once and future king. He would come to realized that magic wasn't evil. He would understand one day. But he was finding that harder to believe as the prick dragged him back to his chambers and made him clean the room from top to bottom before letting him go.

* * *

"Shh!" Arthur held his hand up and stopped the group's advance, motioning for everyone to fan out and surround the figure he had saw dart behind the bush. Merlin had to suppress the urge to groan, he hated these hunting trips, all they ever did was run around and shoot at animals, he didn't understand why the knights loved it so much. Arthur raised his crossbow and aimed at the figure, finger twitching on the trigger before he heard a shout.

"Sire! It's a child!" Leon called.

Arthur lowered his crossbow, handing it over to Merlin, "Come out from there," He said in an authoritative tone.

A small boy walked out from behind the bush, a black cloak covering most of his body but it was clear that he was skinny, likely malnourished. Merlin immediately felt a sense of pity for the boy, wondering what he was doing in these dangerous woods.

Clearly the king was thinking the same thing so he voiced his question, "What are you doing in these woods?"

The boy looked nervous, glancing between the knights surrounding him, all of which had begun to move back towards Arthur, "I'm trying to find my village. We were attacked and some escaped. I hid in a tree until the danger was gone."

Arthur's brows furrowed, he hadn't heard of any attacks recently, and he certainly didn't think that he was in such a bad way with anyone that they would attack his kingdom. Except maybe with… Morgana. "Who attacked your village,"

The boy turned and faced one of the knights, Sir Ector, raising his skinny arm and pointing at him, "He lead them, him and other men with swords and capes,"

Confusion swept over them all for a moment before Arthur remembered an attack he ordered a few days ago, "You're a druid?" Nearly all of the knights gripped the handles of their swords, a few of them actually drawing them.

Merlin felt the color drain from his face at this new information. One of the knights lead an attack on a druid camp? Why? Why would Arthur approve that?

Arthur's jaw was set, staying silent for a moment after the boy nodded, "Kill him, we don't need any more sorcerers in Camelot,"

"Arthur!" Any advancements the knights had made stopped when Merlin yelled at the king, "He's just a boy, you can't possibly think there's any evil in him!"

"No I don't, but I didn't believe Morgana would ever have any evil in her either," Arthur countered, his gaze steely and unfeeling.

Merlin couldn't believe what he was hearing, Arthur, the once and future king, the man who was meant to bring peace to Albion and bring magic back to the land was sentencing a child to death just for being born a druid.

"Emrys, please help me," Merlin froze when he heard the boy speak those words, the death of someone so innocent crashing down on him even harder than before.

"Who is Emrys? Who are you talking about? Another sorcerer?" Arthur asked quickly, not going to let and sorcerer walk free.

"Arthur, are you mad? You're going crazy about magic, just like your father!" Merlin said, trying to convince him to leave the boy alone. He felt like it was his duty, they were kin, he and the druids would always look out for each other.

"Magic is evil Merlin, you know that, the day magic is allowed is the day that Camelot falls," The way Arthur said it was almost a snarl, shocking Merlin to the core. He turned his gaze back to the druid boy, drawing his sword, "Tell me who Emrys is and I might consider letting you live if you vow to stop practicing magic,"

"Emrys is the man that will bring magic back to the lands and end the suffering of my people. He will bring peace to Albion and he is more of a man that you will ever be." The boy said, clearly not about betray Merlin.

Merlin felt his heart ache as he watched the knights approach the druid boy, some looking hesitant, others eager, all Merlin could see was people he thought were his friends about to murder an innocent boy. His feet were moving before he could even think about what he was doing, standing in front of the boy, pushing the child behind him where he would be safe. "Arthur, you need to rethink this, this is not the right thing to do and you know it!"

"Merlin get out of the way," Arthur ordered, he could see a few of his knights faltering, Leon, Elyan, Lancelot, Gwaine, and Percival had already lowered their weapons. A voice in the back of his mind that sounded a lot like his father told him to strike Merlin down too, but that was the last thing he wanted to do. "Someone grab the idiot, then kill the boy,"

The knights only made it forward a single step before Merlin's hand came up instinctively, his eyes bursting with a golden fire, sending each knight who posed a threat flying back at least ten feet. Arthur looked positively shocked, unable to do anything but stare at Merlin.

Merlin's heart was racing in his chest, his rage having all but vanished as he realized what he just did. All this time he had been on Arthur's side, standing beside him, protecting him, making sure he would be there to fulfill his destiny. Now, Merlin was standing on his own, in fact, he was standing against Arthur.

"I'm sorry my lord, I tried so hard to believe in you but I will not stand by and watch you become your father, I'm afraid that would be too much for me to bear. I wish both you and Camelot luck but we shall not be sharing destinies any longer. Farewell my friends," He said as he glanced at the knights whom he'd come to consider his family. And yet he felt magic surge through his veins, inviting him to let go and finally stop hiding his power. The ancient language felt as natural on his lips as English when he spoke it, causing a burst of wind taking him and the druid boy away from that place.

* * *

 **Hey guys! So that was pretty much ALL build up to what's going to happen. Arthur's pretty crazy! But Merlin hasn't given up on him quite yet. Do you think Arthur will change after learning his best friend is a magic user? Or will he keep pushing past Merlin's limit? Comment what you think of it so far and if it's worth an update!**


	2. Chapter 2

Merlin found himself in the Valley of the Fallen Kings, still holding onto the boy protectively. He looked down at the child, sighing softly. His whole life had just been turned upside down but it didn't feel like the world was ending so he supposed it was the right choice. Perhaps he will be happier among the druids than he ever was in Camelot.

"Thank you, Emrys," He boy said, his head pressing against Merlin's stomach, still holding onto him after being teleported.

"You can call me Merlin if you'd like," He said with a kind smile, "Now," He said, crouching down so he was eye level to the child, "Let's find your village and bring you back to your people huh?"

The child smiled brightly and nodded his head, hugging Merlin tightly. Merlin couldn't imagine how protecting such an innocent child could be the wrong choice.

* * *

"Find him! I don't care what you do or at what expense, I want him in the dungeons," Arthur raged to the round table. He'd become more and more unstable as time went on after his father's death and everyone had noticed.

"Sire, perhaps you might rethink this." Leon cut in, he'd always been one of Arthur's closest friends but he'd never seen him this way, "It's Merlin we're talking about, he has no reason to return and cause us harm,"

"He's a sorcerer, that's reason enough," Arthur snapped, clearly feeling threatened by Merlin.

"And a powerful one to be able to do what he did out there." Gwaine pointed out, "Don't you think he would have done something sooner if he had intended to harm us?"

Arthur pinched his chin as he thought, nodding his head absentmindedly, "You're right, he's too powerful to leave to his own devices,"

"Sire!" Lancelot butted in, as loyal as he was to Arthur, Merlin was a friend to all of them, "What has gotten into you? You can't possibly think that Merlin means to harm us,"

Arthur frowned and glared at Lancelot, "Don't cross me now, Lancelot. If you lot won't find him then I'll send a group of knights that will."

The quickly shut everyone up, as much as they didn't want to hunt down Merlin, a knight that didn't know him would probably hurt him, "I will lead the exposition then," Leon said quickly before any of the more eager knights could offer, "I'll need two candle marks to gather a group and prepare to leave,"

Arthur nodded his head in satisfaction, waving his hand to send everyone away. Almost immediately after exiting the room the knights were in an uproar.

"Leon! We can't hunt Merlin, it's not right!" Lancelot said as he and the rest of the knights followed after him.

"I know that," Leon said with a sigh, turning round to face the congregation of knights who still considered Merlin a friend, "And we're not going to hunt him, we're just going to find him and talk to him, okay? If push comes to shove we can tell Arthur that Merlin is dead,"

"I'm going with you," Gwaine said instantly. He'd always liked Merlin better than Arthur and right now Arthur was giving him even more reason to dislike him.

"Fine, you and Lancelot, but the rest of you need to stay and keep Arthur in line," Leon said, watching as everyone nodded and went off to their jobs. He sighed as he watched Arthur storm out of the throne room, muttering under his breath, "Arthur, what happened to you, my friend?"

* * *

Merlin honestly couldn't remember a time when he had smiled so much. Maybe when he was a child and lived with his mother, using his magic to entertain the both of them, but he was insanely happy living in the small druid village. He could use his magic whenever he liked and everyone there was constantly praising him and telling him how wonderful he was. Some asked him how he planned on uniting Albion but he normally avoided that question.

Of course, that happiness came to a halting stop when he sensed a stranger in the area. He'd gotten into the habit of meditating everyday and it helped him become much more aware of his surroundings. He was able to extend his magic out into the environment around him and use it to see for miles in every direction. It was a calm, peaceful feeling that ended the moment he felt someone else, someone who wasn't a druid.

He stood up abruptly, startling a couple people who were sitting by the campfire with him. Without a word, he walked towards the forest, his magic creeping out to find the stranger, "Leon," His lips were pressed into a thin line as he watched the knight turn around, jutting out his sword before lowering it upon realizing who it was.

"Merlin, thank god, we've been looking everywhere for you!" Leon said with a relieved sigh, "Arthur's gone crazy, he's sending out search parties left and right to find you,"

Merlin was confused, rightly so. There was no way that Arthur Pendragon was having second thought about condemning all magic, that just wasn't who Arthur was, "He wants me back in Camelot?" He asked hesitantly, still wary of the knight despite them being friends.

"Yes," Leon said, stepping closer to Merlin, "And I don't think he will stop until he finds you. I understand if you don't want to come back, I am capable of feeding him a story that you were found dead, but if you would like, Gwaine and Lancelot are in the area too, we'll take you back."

Merlin couldn't believe that Arthur had a change of heart, maybe he was wrong about Arthur, maybe their friendship was strong enough that Arthur would begin to accept magic, "No, of course I'll come back, I belong in Camelot after all," He said, beginning to smile, "I didn't quite realize how much I've missed you lot until now. I mean, it's nice out here where I can be myself but I suppose I can be myself among you lot now,"

"Merlin!"

Merlin turned around only to be enveloped in a tight hug. It took a moment for him to realize that it was Gwaine who was enveloping him, "It's nice to see you to, Gwaine," He said with a small laugh.

Gwaine laughed as well, pulling away to look at Merlin, "You're not going to magic me for touching you, are you?" He joked, causing Merlin to roll his eyes and give the knight a friendly shove.

"Alright guys, let's find Lancelot and head out," Leon said, jerking his head in a motion to follow as they set off back towards Camelot.

* * *

"Sire, sorcerer Merlin is here to see you," Those were the words Arthur had been waiting to hear for days, almost a week now.

"Thank you, bring him in," Arthur said with a stiff expression on his face. The frown on his face deepened when he saw Merlin walk into the room, looking as jolly as he always did. The bastard, lying to all of them for god knows how long.

"Arthur, they told me you've been searching for me with no regard for the price," Merlin said, a smile gracing his lips, a smile that made Arthur furious.

"Yes, letting a sorcerer walk is treason after all and the king should be the last person to commit treason," Arthur said bluntly, watching as Merlin's smile faded, that's better.

"What? That's the only reason you wanted me back…?" If Arthur had known any better he would have thought that Merlin was heartbroken. "But I thought-"

"No, I don't want to hear a word you have to say," Arthur said, cutting him off, "Take him to the dungeon to await trial, now," He ordered, waving over the guards that stood at the door.

"What?! Arthur, what are you doing? What has gotten into you?" Merlin barely had time to struggle as he was pulled out of the room.

* * *

Merlin's hands were drawn into tight fists in the cell. The last thing he wanted to do was hurt anybody and consequently, that lead to him with magic canceling shackles around his wrists. Of course he had no doubt that he would be able to get out of them but he was afraid that after he did, he would go on a rampage.

So instead he sat on the cold floor waiting for either himself to calm down or someone to come get him. The latter happened to come first.

"Merlin, what happened?"

Merlin looked up to see Gwaine rushing towards the bars with a ring of keys in his hand. He was sure that no one would give Gwaine of all people the keys to his cell and it warmed his heart to know that at least Gwaine was still his friend, "Arthur's gone ballistic. He also seems to be under the impression that I'm a sorcerer,"

"You're not?" Gwaine asked as he unlocked the door to the cell and crouched down next to Merlin to see which key fit in his shackles.

"I suppose I can't blame you lot for not knowing anything about magic, it has been outlawed for years now, but a sorcerer is someone who chooses to practice magic, a warlock is someone who is born with magic, like myself," Merlin explained, a golden fire crackling in his eyes for a moment before the shackles unlocked on their own, crumpling to the ground.

Gwaine all but jumped back, blinking a few times to make sure he was seeing things right, "How did you do that? Those shackles were magic-canceling."

"For a sorcerer," Merlin answered, "For a warlock, magic is a part of our very being and it cannot be taken away so easily,"

Gwaine was still pretty shocked but didn't comment on it any further, just tossing the shackles to the side and standing up, "Come on, let's get you out of here,"

"You know that's treason, right?" Merlin said with a raised brow, the last thing he wanted to do was to get his friends in trouble.

"I've been exiled before, and princess is really starting to grate on my nerves anyway," Gwaine said with a shrug, taking Merlin's arm and helping him stand up, "Come on, the guys can't protect the way out forever,"

"The guys?" Merlin questioned, stumbling a bit as Gwaine pulled him out of the cell.

"You didn't think we all abandoned you, did you? Lancelot, Leon, Elyan, and Percival are guarding the path out of here," He said with a grin pulling Merlin through the dark halls.

* * *

"Merlin, you've been sitting there for hours, don't you know where it is yet?" Gwaine whined, staring at Merlin who was sitting on the forest floor with his eyes closed.

"We've only been here for ten minutes," Merlin said without opening his eyes, trying to probe around the area for signs of life. He could have sworn the village was around here somewhere.

"Well I'm going to take a look around with my eyes like a normal person," Gwaine said, standing up and walking off in a random direction they haven't been in yet. It wasn't another ten minutes before Gwaine came rushing back, "Merlin, you should see this,"

Merlin's eyes opened and were met with a distressed looking Gwaine. He frowned in worry, "What is it?" He asked as he stood up, stumbling when Gwaine grabbed his arm and pulled him in the direction he came, "Gwaine, what-" He abruptly cut himself off when he saw the village he was looking for,

Riddled with bodies.

"No…" This was why he couldn't find anyone… they were all dead, "Who would have done this…?" He asked, his eyes filled with horror as he walked through the mess of bodies.

Gwaine was silent as he walked up to Merlin with a torn scarlet cape draped over his arms, it belonged to a knight of Camelot.

Tears formed in Merlin's eyes, all but falling to his knees when he spotted the young druid boy he risked his life saving, dead on the ground, his eyes still wide open in shock. Merlin let the tears roll down his cheeks as he closed the boy's eyes, mourning the loss of the people who had been so kind and generous to him over the last few days, "How could Arthur do this…?" He whispered, trying to come to terms with what was happening. He had to close his eyes to shield himself from what was happening, he didn't want any of this to be real.

"He hasn't been himself lately, we all know that," Gwaine said quietly, not wanting to upset Merlin further.

Merlin's eyes snapped open with golden rage burning in his eyes, "He can't be left to his own devices any longer. I'd once believed that he would become the Once and Future King with a little gentle guiding but it doesn't seem that's possible." He stood up abruptly and turned to face Gwaine, "I will be hurting people, I will more than likely be hurting Arthur. If you don't want any part in that, I want you to leave so you don't have to be a part of this,"

Gwaine couldn't help but grin and pat Merlin on the back, "It's about time you grew a pair, I'm with you the whole way, Merlin,"

The warlock blushed a little bit but smiled, he was grateful to have a friend like Gwaine.

* * *

 **Dun, dun, dun... You know, that sound effect thing? No? Just me? Okay, this is my next chapter where the ball gets rolling and Merlin finds his reason to hate Arthur and learns to unleash all of his power. My idea is that he's always been super crazy powerful but living in Camelot put a lock on his magic but since he left he learned how to use it right. Anyway! I hope you liked it and please leave reviews! Reviews make me happy!**


End file.
